The present invention relates to an apparatus designed to be mounted on an agricultural sprayer with the purpose of decreasing the drift and improving the deposition, penetration and uniformity of distribution when applying liquids such as pesticides and liquid plant nutrients used in agriculture, horticulture and forestry.
Application and handling of pesticides is a delicate task which may cause substantial costs, both economical and environmental. Consequently, it is of outermost importance for a long-term efficient and persistent production, e.g. food supply, that the distribution of pesticides is executed in an efficient and safe way. For the application method to meet these needs it is required to:
Reduce environmental impact: Decreasing the environmental pressure exerted by the chemicals requires reduced doses and decreased drift and leach. To make it possible to reduce the doses without forgoing the final result an efficient application method is required which ensures optimal chemical deposition onto the spray target.
Reduce costs: The modern application method required for better utilization of the chemicals must also be as cheap as possible for the decreased usage to result in reduced overall costs. This is a prerequisite of the method to result in common use.
Application of pesticides may be executed with a real spraying with agricultural sprayer, band spraying or contact application. A real spraying implies that the whole field is prepared/sprayed while band spraying means that only one band including the planting row or the space between the planting rows is sprayed. Contact application means that the pesticide is transferred by direct contact. This type of control occurs only to a limited extent and only in specific control situations. Conventional methods for a real spraying comprise agricultural sprayers equipped with hydraulic sprayers uniformly spaced at a distance of 50 cm along the boom. When spraying, only a fraction of the sprayed liquid reaches the noxious object. Portions of the spray liquid will drift with the wind or evaporate, and some portions will land on the ground or on parts of the plants where the liquid has no effect. Different estimations of the fraction of the sprayed liquid which actually has effect, i.e. reaches the spray target, varies between 0,1 to 30%.
The most important element in reducing the dose, and decreasing the environmental impact, is to achieve good deposition onto the spray target. This is difficult to accomplish with conventional methods because of the following reasons:
High boom level: High boom level, 50 cm above the ground, is required to achieve a uniform liquid distribution. This increases the risk for drift. A cause of increased drift is, among other things, that the droplets are exposed to the wind during a long time period on their way from the nozzle to the spray target. This, in combination with the fact that the wind velocity increases exponentially with increasing distance from ground, makes the boom level an important contributor to the drift.
Boom movements: Boom movements is one of the most important causes for a non-uniform liquid distribution. Both horisontal and vertical boom movements may cause substantial dose variations over the field. The non-uniform liquid distribution results in poor treatment effect, which must be compensated by an increased dose. In addition, there is a risk of damage on the crop in places which receive the highest doses. The vertical boom movements involve also often damage on the nozzles when these are forced into contact with the ground and crop.
Drift: The drift is a problem of great concern which is affected by weather conditions, spray quality and exposure of the droplets to weather influence. At given weather conditions, the only possible measure to reduce the drift with conventional methods is to choose a coarser spray quality. Conventional methods normally use medium or coarse spray quality (big droplets). Coarser spray quality involves lower degree of coverage and therefore lower pesticide control effect which must be compensated with higher dose.
Penetration: With conventional application methods the droplets have low velocity when they reach the stand, which impair the penetration into stands with high density. The droplets also fall vertically which gives poor deposition under leaves and onto vertical surfaces. The penetration is of special importance for instance in control of Phytophthora infestans on potato. Phytophthora infestans on potato causes great losses and the fungus is often hiding in high density stands.
In application with conventional methods, liquid quantities in the order of 200 l/ha (litres per hectare) is often recommended in application onto low crop stands and 300-400 l/ha onto high density and high crop stands. These relatively large liquid quantities decrease the efficiency of control because of the increased number of refillments required, which increases the costs and decreases the spray time. It is not rare that refillments, including transports, occupy one third of the total treatment time. The weather is a very limiting factor for chemical control and the number of opportunities to spray are few. Consequently, it is of great importance that the spray opportunities are efficiently utilized. The possibility to conduct control at optimal time also maximizes the biological effect and facilitates dose reduction.
Traditional spray methods have been used since the beginning of chemical control by the end of the 19th century, and it is the purpose of the present invention to solve the accompanying problems. Below, band spraying, contact application and the conventional methods of areal spraying with agricultural sprayer will be described. Regarding areal spraying also more modern methods, intended to solve the problems of conventional areal spraying methods though with unsatisfactory solutions, will be described.
Conventional methods imply that the nozzle/nozzles is/are positioned and mounted on the boom with downwardly directed spray direction.
Band spraying means that a band, including the planting row or the space between planting rows, is sprayed. The method is used for row growing crops such as sugar-beets, strawberrys and outdoor cultivated vegetables. Band spraying may be performed with a modified agricultural sprayer or a separate suitably equipped machine. In order to keep the distance between the ground and the nozzles, one or more, at a constant level, the nozzles are often mounted on runners, such as described in U.S. Pat. No. 2,580,145 and German patent no 1482350. In some cases also tunnels are used to protect both the spray shower from external influence and the portions of the ground/crop not to be sprayed.
In case of contact application, pesticides are transferred to the target by direct contact using ropes, sheets or rolls. Contact application is used, for instance, to control late high-growing weeds in different crops, weeds in watercourses and during control in connection with harvesting with combine. The precondition of using this method, and accomplishing the selective weed control, is that the control object has a deviating, higher height than the surrounding. This makes this method only applicable in very specific control situations.
Irregularities in the liquid distribution when using conventional methods are to a great extent due to boom movements, both horisontal and vertical, while running. These movements depend on the dynamical characteristics of the boom and the sprayer and may to some extent, particularly in the vertical direction, be damped by the use of suspension attachments, as described in German patent no. 2359400.
New application methods used today are often based on some sort of air assistance. Air assistance may be classifed according to two principles, internal or external air assistance.
Internal air assistance means that air is added (by means of a compressor or a fan) inside the nozzle so that the air, together with the liquid, contributes to the droplet formation itself. Independent of the actual method, the principle of internal air assistance makes it, under some circumstances, possible to keep the size of the droplets constant within a certain range, independent of the water flow. In one application of internal air assistance, the required amount of liquid and size of droplets are loaded into a spray computer which controls air and liquid pressure. These systems use conventional deflector nozzles and the recommended boom level is 50 cm or higher. In another application of internal air assistance, nozzles are used where the air flow passes a wing, over which the liquid is led, and forms a film of liquid. The droplets are formed when the liquid is ripped off the edge of the wing by the air jet. The nozzles are spaced with a distance of 16 cm and the recommended boom level is higher than that for conventional methods.
External air assistance means that the air is added (normally by a fan) outside the opening of the nozzle. The formation of droplets is made with conventional nozzles, and the purpose of the air addition is to increase the speed of the droplets towards the spray target. The velocity of the droplets is increased by direct influence of the air jet, or indirectly as the air jet creates a downwardly directed injector effect towards the spray target. When applying methods which use direct influence one also tries to create an air shield which shelters from air drift. The recommended boom level is the same as, or higher than that, for conventional methods.
Another principle includes enclosing of the spray fan against the ground or crop in order to prevent the wind to affect the spray fan.
On the market there were earlier also crop openers available which opened up high crop stands and facilitated lowering of the boom. However, the constructions of the crop openers resulted in strong forces upon the boom construction which caused the booms to break. The crop openers therefore have disappeared from the market.
From the drift point of view it is possible to achieve a positive effect with some applications of internal and external air assistance. However, the result depends to a great extent on the particular settings used, and, in some cases, settings decreasing the drift may result in a risk for poor biological effect. Incorrect settings of air quantities and size of droplets may even result in increased drift.
External air assistance, together with enclosed spray fan and crop opener, may increase the deposition into the crop substantially compared to conventional methods, but often at the expense of increased deposition onto the ground.
As shown above, the current methods have not satisfactory and sufficiently solved the problems of boom movements, boom level, deposition and wind drift. The methods are considerably more expensive than traditional methods and only in exceptional cases is it possible to after-mount the systems on an existing sprayer. The systems require extensive knowledge and carefulness for correct adjustment and all systems, except the one with enclosed spray shower, have at least one more demand for adjustment compared to conventional methods. Some of the systems also require that the adjustments are changed during work depending on wind direction and wind-force.
Conventional methods, as used herein, comprise all prior art.
The general purpose of the present invention is to provide an apparatus for application of liquids, such as pesticides, which decreases the drift and improves the deposition onto the spray target and improves the spray uniformity, minimizing the consumption of liquids (agrochemicals), decreasing the pressure on the environment and reducing the costs in agriculture. The apparatus is to be after-mountable on a conventional agricultural sprayer without requiring further adjustments. The expression xe2x80x9cliquidsxe2x80x9d in the present application refers primarily to chemical and biological pesticides, such as micro-organisms, different types of plant nutrients and the like, but also all kinds of liquids which can be applied by means of an agricultural sprayer and the apparatus of the present invention.
The purposes of the invention are achieved by a movable mounting of the nozzles, not on the boom but on a movable, separate part according to the invention, which gives in when making contact with ground or crop. The nozzles will therefore be at. approximately the same distance above the spray target even if the ground is uneven and/or the spray boom is moving vertically. The distance between the nozzles and the spray target can therefore be shortened which decreases the drift. Without this resilient feature, there is an evident risk that the distance between the nozzles and the spray target becomes too short with non-uniform liquid distribution and/or damage on the sprayer as a consequence. In high crop stands the apparatus will open up the stand, which also improves the penetration into stands with high density. The spring system also decreases the risk of horisontal boom movements to impair the deposition.
The invention relates to, besides providing the apparatus described in detail below, the use of this apparatus and a method for producing the central, movable part, below referred to as (A). This part provides a simple construction since it is made in one piece, with low production cost and sufficiently low weight to be mountable on existing booms at used agricultural sprayers.